Preparation and Properties of Alkane Adsorptive Separation Materials via π-Complexation

Cu(I) is a highly effective π-complexing agent for olefin/paraffin separation. In this study, a confined space strategy was employed to enhance Cu(I) stability in Cu-modified MCM-41 by introducing a porous silica layer, which prevents Cu aggregation during high-temperature reduction. The optimized Cu-4Si(R) material achieved a Cu(I)/Cu(II) ratio of 2.52, compared to 0.82 in unmodified Cu(R). The introduction of the silica layer increased 1-hexene adsorption from 1.05 to 1.42 mmol/g and selectivity from 5.74 to 13.62. The confined structure also improved Cu(I) stability in air. As a result, the material maintained an adsorption capacity of 0.91 mmol/g after 4 days and 0.79 mmol/g after 4 cycles (24.77% and 20.25% higher than that of the unmodified material). Molecular simulations revealed that the adsorption binding energy of 1-hexene on structurally optimized Cu-4Si(R) decreased significantly by 14.3 kJ/mol. This strategy significantly boosts adsorption capacity, selectivity, and cyclability for olefin/paraffin separation.